Chestnut Street Bridges

Glossary

Curious about an engineering or construction term used on this website? Scroll down and click on the term you would like explained. If you have another question about this project or about anything related to roads or bridges, check our Frequently Asked Questions or Contact Us. Thank you for your interest in this infrastructure improvement.

 

Abutment

A retaining wall on opposite sides of a bridge or viaduct that supports the deck beams or girders and tie the structure into the approaching roadway.

Beam

A horizontal structure member supporting the bridge deck and the traffic load, usually smaller than a girder.  Can be pre-stressed concrete or steel.

Bituminous Paving

Asphalt or blacktop paving material.

Column

A vertical, structural element supporting the bridge deck and the traffic load.

Deck

The roadway portion of a bridge, including shoulders, usually composed of reinforced concrete.

Expansion Joint or Expansion Dam

A meeting point between two parts of a structure that allows for movement due to expansion or contraction caused by temperature changes.  Commonly visible on a bridge deck as a hinged or movable connection.

Federal Highway Administration (FHWA)

An agency within the U.S. Department of Transportation that supports State and local governments in the design, construction, and maintenance of the nation’s highway system (Federal Aid Highway Program) and various federally and tribal owned lands (Federal Lands Highway Program). More here.

Fill

Earth, stone or other material used to raise the ground level, form an embankment or fill the inside of an abutment.

Footing

Part of the substructure or foundation that rests directly on the soil, bedrock or piles.

Formliner

A type of Wall Treatment used to create designs on concrete walls, making them more attractive walls for highways, neighborhoods and parks. Formliners come in many different shapes and designs, and can produce a variety of textures and designs on concrete.

Formwork

A temporary structure that encloses the reinforcing steel (re-bars) and supports freshly placed concrete and allows it to harden into the desired shape.

Functionally Obsolete

A functionally obsolete bridge is one that was built to standards not in use today, such as narrow lane and shoulder widths, inadequate vertical clearance, etc. These bridges are not inherently unsafe.

Girder

A horizontal structure member -- usually steel -- supporting the bridge deck and the traffic load.

Jersey Barrier

A low, reinforced concrete wall wider at the base, tapering vertically to near mid-height, then continuing straight up to its top. The shape is designed to direct traffic back toward its own lane of travel and prevent crossing of a median or leaving the roadway.

Parapet

A low wall along the outside edge of a bridge deck.

Pile

A long column driven deep into the ground to form part of a foundation or substructure.

Pile Driver

A machine that repeatedly drops a heavy weight on top of a pile until the pile reaches solid soil,  rock a point of friction where it cannot be driven further.

Pre-Cast Girder or Beam

Girder or beam fabricated off-site using reinforced concrete and post -tensioning cables that create a slight bend in the member that straightens out under the deck and traffic load.  They are shipped to the construction site by truck and hoisted into place by cranes.

Reinforced Concrete

Concrete reinforced with steel bars or mesh embedded in it for increased strength in tension.

Span

The horizontal space between two supports of a structure. Also refers to the structure itself. May be used as a noun or a verb.

Specifications

A document that explains all material and construction requirements of the bridge structure to be constructed. Also Specs.

Streetscape

A combination of the elements within and along a street and sidewalk that define a street's appearance, identity and function, including street furniture (benches, trash cans, etc.), landscaping, trees, sidewalks and pavement designs, among others.

Structurally Deficient

Bridges are considered structurally deficient if significant load carrying elements are found to be in poor condition due to deterioration.  A "structurally deficient" bridge is not necessarily unsafe. When left open to traffic, these bridges typically require significant maintenance and repair to remain in service.  They are often posted with weight limits to restrict the gross weight of vehicles using them.

Substructure

All parts of a bridge or other structure that support the superstructure, including footings, pilings, abutments and piers.

Superstructure

The superstructure consists of the components that actually span the bridge crossing, including structural members (girders, beams, etc.), the bridge deck, parapets, handrails, sidewalk, lighting and drainage system.

Viaduct

An elevated bridge-like structure that carries a road or railroad over lower ground.

Weight-posted Bridge

Based on its design or its condition, a bridge that does not have the reserve capacity to accommodate most vehicles over legal weights as posted on a sign, but can still safely carry legal weights.

Spandrel Wall

A spandrel wall is the space on a bridge between two arches or between an arch and a rectangular enclosure.